A rule that requires New York City fast food restaurants to post calorie information on their menu boards has not changed consumer habits in low-income neighborhoods, according to a study published on Tuesday.

While half of consumers surveyed said they noticed the labeling, and about a quarter of those said they made different choices as a result, a review of fast food purchases showed habits remained the same, said the study, published in the journal Health Affairs.

In July 2008, New York became the first U.S. city to mandate that fast food restaurants post calorie counts in large type on menu boards. The system has since become a model for similar rules intended to combat obesity and promote good nutrition being implemented in California, other parts of New York state, the cities of Seattle and Portland, and elsewhere.

Brian Elbel, a professor at the New York University School of Medicine and a lead author of the study, which was conducted in low-income neighborhoods with high minority populations, said that more research needed to be done.

Though the introduction of calorie labels did not change the number of calories purchased, a combination of public policy efforts are likely necessary to produce a meaningful change in obesity, Elbel said.

About one-third of U.S. adults are obese, a condition that increases the risk of heart disease, diabetes, cancer and other medical problems.

In compiling the data, researchers at New York University and Yale University analyzed fast-food purchases by 1,156 adults at Burger King, Kentucky Fried Chicken, McDonald's and Wendy's immediately before and after the rule went into effect.

The percentage of people aware of the calorie information increased from 16 percent to 54 percent, but the number of calories purchased was slightly higher than before the rule was implemented, researchers found.

Nearby Newark, New Jersey, where menu labeling is not required, was used as a control group.

New York City Mayor Michael Bloomberg said the study may have been done too soon after the rule went into effect and before all fast food restaurants were in compliance.

The city will release its own study in several months using a sample size of 12,000 and covering a range of neighborhoods.

At least the public has information and that's the government's job -- to make sure that the public has information, Bloomberg told reporters on Tuesday.

But once again, this is America and you have a right to eat what you want to eat, he said.